Traditional slash jackets are made from a single sheet of paper folded to provide front and back panels which are attached to each other. The back panel is generally rectangular, and the top portion of the front panel is cut off diagonally. The bottom and usually both lateral sides of the front and back panels are adhered to each other, forming a compartment for paper storage between the panels with an opening at the top of the jacket and with closed sides and bottom. The cutout section of the front panel permits a portion of papers kept in the jacket to be viewed, while the rectangular back panel and the full length closed side of the slash jacket securely retain the contents in the jacket.
Some slash jackets are made without any perforations. Others slash jackets, however, include a perforated edge for receiving binder rings, enabling the jacket to be bound in a binder, such as taught in U.S. Pat. No. 3,528,602. Papers stored in a slash jacket of this type may shift towards the perforated edge, requiring that they be moved back away from that edge before the jacket is placed within a binder. Also, binders that have such an edge must be made significantly wider than the width of the papers they are meant to carry to provide the necessary space for the stored papers in addition to the space required for the perforations.
In addition, traditional slash jackets, as taught in the '602 patent, are shaped to contain a only thin stack of papers and are not readily expandable. File pockets, on the other hand, such as disclosed in U.S. Pat. No. 5,161,731, are constructed to carry a thick stack of papers. The folder disclosed in the '731 patent has front and rear panels connected to each other along the bottom and lateral sides of the folder by gussets. The gussets along the sides of the folder are equally long, and the front panel extends straight across the top of the folder. These gussets allow the folder to expand, to fit a variable paper stack thickness.
U.S. Pat. No. 4,109,850 teaches a folder with an expandable pocket formed from a sheet. A front and a back of the pocket are connected by accordion type expansion zones located only on the bottom and one side of the pocket. The front is made from two overlapping portions that are not fixed to each other, but are connected by a slidable tab. This sliding tab arrangement, however, is relatively weak, and relies on a hinged leaf to cover the pocket.